Here are some of the latest health and medical news developments, compiled by the editors of HealthDay:

As Jobs Got More Sedentary, Americans' Waistlines Grew: Study

A new study suggests that a move to more sedentary jobs may be another big factor behind the U.S. obesity epidemic.

Research published Wednesday in the journal PLoS One reviewed changes in the American labor force since 1960. The study found that jobs requiring some sort of moderate physical activity have dropped from 50 percent of the labor market in 1960 to just 20 percent today.

"If we're going to try to get to the root of what's causing the obesity epidemic, work-related physical activity needs to be in the discussion," lead author Dr. Timothy S. Church, an exercise researcher at the Pennington Biomedical Research Center in Baton Rouge, La., told The New York Times. "There are a lot of people who say it's all about food. But the work environment has changed so much we have to rethink how we're going to attack this problem," he added.

According to the authors, a shift from a job requiring moderate physical activity to one that is wholly sedentary, or requiring only light activity, means a drop in daily energy expenditure of 120 to 140 calories per day.

While a decline in the percentage of Americans involved in farming-related jobs has contributed to the trend, Church said that losses in the manufacturing sector have mattered, too.

"You see the manufacturing jobs plummet and realize that's a lot of physical activity," he told the Times. "It's very obvious that the jobs that required a lot of physical activity have gone away."

While it's not likely that society will shift back to more active jobs, some employers are trying innovative approaches to help workers get more active on the job. According to the Times, offices can be redesigned to encourage walking, including placing printers far from desks or encouraging face-to-face talks versus e-mail correspondence.

-----

Groups Sue FDA to Ban Certain Antibiotics in Animal Feed

A number of environmental and health-advocacy organizations have launched a lawsuit to try and force the U.S. Food and Drug Administration to ban the use of two types of antibiotics in livestock feed, the Wall Street Journal reported on Wednesday.

The groups charge that the widespread use of penicillin and tetracycline antibiotics in animal feed is contributing to bacterial resistance to antibiotics that people use to fight dangerous infections. They say the government has failed to stop the practice.

"Approximately 80 percent of all antibiotics used in the United States today are used in livestock," the groups said in the suit, the Journal reported. "Most of these drugs are not used to treat disease. Instead, they are given to healthy animals in their feed or water, both to promote faster growth and to prevent infections."

According to the newspaper, the FDA said that livestock raised in the United States consumed almost 29 million pounds of antibiotics, with about 74 percent given through the animal's feed.

Groups involved in the suit include the Natural Resources Defense Council, Center for Science in the Public Interest, Food Animal Concerns Trust, Public Citizen, and Union of Concerned Scientists. They filed the suit Wednesday with the U.S. District Court for the Southern District of New York.

Doug Wolf, president of the National Pork Producers Council, called the suit "spurious," the Journal said.

FDA spokeswoman Siobhan Delancey said the agency does not comment on pending litigation.

-----

Most ER Visits for Sports-Related Concussions Involve Kids

More than 80 percent of all emergency room visits for sports-related concussions involve children under the age of 18, a new U.S. government study shows.

In a report released Wednesday, the Agency for Healthcare Research and Quality (AHRQ) found that almost 40,000 youths wound up in the ER and were diagnosed with the condition in 2008 alone.

Those between the ages of 14 and 18 accounted for the lion's share of these head injuries, at 58 percent, while 17 percent were between the ages of 11 and 13 and another 7 percent were aged 6 to 10. The AHRQ researchers also found that 21 percent lost consciousness briefly, while another 12 percent blacked out for a longer period of time.

The good news was that 52 percent of these patients did not lose consciousness, and 95 percent did not have to be admitted to the hospital. Boys represented almost 80 percent of the injuries.

These young patients often wound up receiving care for other injuries, for everything from pulled muscles and sprains to skull fractures.

-----

Study Links Spinal Fusion Product to Male Sterility

A study from a Stanford University surgeon released Wednesday suggests that a widely used growth protein used in spinal fusion procedures may heighten men's risk of sterility, The New York Times reported.

The product in question is Infuse, a bioengineered bone growth protein from Medtronic that has been used in spinal anterior lumbar fusion procedures since 2002, the Times explained. While the Infuse label does list sterility-linked complications as a possible side effect, studies sponsored by Medtronic have attributed the complications to the surgery, not Infuse.

But Dr. Eugene J. Carragee, a Stanford surgeon, reported in the online edition of The Spine Journal Wednesday that men who received Infuse developed temporary or permanent sterility much more often than men who received a bone graft, an alternative treatment used to fuse vertebrae. That study was based on 240 men he treated several years ago.

"It is important that men who are considering having children have the opportunity to weigh the risks of the various available procedures," Carragee told the Times.

Over 80,000 people undergo anterior lumbar fusion procedures each year, the newspaper said, and about half of these procedures use Infuse. According to Carragee's study, five of 69 men who received Infuse developed a complication linked to sterility, compared to one of 174 men who got a bone graft.

The two authors of the prior, Medtronic-funded trials defended their findings, saying the number of men in their clinical trials who had developed sterility did not reach statistical significance. Surgeons Dr. J. Kenneth Burkus and Dr. Thomas A. Zdeblick also noted that Carragee's study was retrospective in nature. Zdeblick told the Times that such studies "are notorious for being misleading."